1. Field of the Invention
The present invention relates to an apparatus for attaching an object; i.e., a printing plate or a blanket, to a printing cylinder of a printing press (hereinafter referred to as an xe2x80x9cobject attachment apparatus of a printing cylinderxe2x80x9d), and to a printing plate and a blanket which can be attached to the printing cylinder by use of the apparatus.
2. Description of the Related Art
Japanese Patent No. 2956026 discloses a conventional apparatus for winding a printing plate or blanket around the outer circumferential surface of a cylinder of a rotary press to thereby attach the plate or blanket to the cylinder under tension.
The attachment apparatus disclosed in Japanese Patent No. 2956026 will be described. A printing plate or blanket (hereinafter generally referred to as a xe2x80x9cplatexe2x80x9d) to be attached to the cylinder has opposite end portions which are bent at respective angles corresponding to an angle formed between a slit for receiving the opposite end portions and the outer circumferential surface of the cylinder. That is, a first end portion of the plate is bent at an angle substantially equal to an acute angle formed between the slit and the outer circumferential surface of the cylinder, and a second end portion of the plate is bent at an angle substantially equal to an obtuse angle formed between the slit and the outer circumferential surface of the cylinder. Further, a large number of square openings are formed in a leg portion of the second bent end portion.
The apparatus for attaching the plate under tension disclosed in Japanese Patent No. 2956026 has the following structure. An axial-extending slit is formed in the cylinder of the rotary press such that the slit opens at the outer circumferential surface of the cylinder and extends radially inward; an axially-extending hole is formed in the cylinder such that the hole continues from the bottom portion of the slit; and an axially-extending tension spindle is rotatably inserted into the hole.
The plate is attached to the cylinder as follows. The first bent end portion of the plate is inserted into the slit to be located on the acute-angle side of the slit. Subsequently, the plate is wound around the outer circumferential surface of the cylinder, and the second bent end portion of the plate is inserted into the slit and attached to the tension spindle. Upon rotation of the tension spindle, the plate is pulled into the slit from the second end portion side, whereby the plate is attached to the outer circumferential surface of the cylinder under tension.
The means for attaching the second bent end portion to the tension spindle is a strip having a large number of elastic rectangular tongues aligned along the strip, such as a comb-shaped plate spring. The strip is disposed in a groove which is formed in the tension spindle and has a V-shaped cross section. The elastic rectangular tongues enter the large number of square openings of the leg portion of the second bent end portion, and their inwardly-facing surfaces come into engagement with the inner edge portions of the openings. More specifically, the base portion of the strip is fixed to the bottom portion of the groove such that the tip ends of the rectangular tongues project from the outer circumferential surface of the tension spindle and such that the tip ends can bend.
After the tip ends of the tongues have entered the openings at the second bent end portion of the plate upon rotation of the tension spindle, the inwardly-facing surfaces of the tongues come into engagement with the inner edge portions of the openings and move angularly, while bending, upon further rotation of the tension spindle. Thus, the tongues pull the plate into the slit by means of their elasticity, whereby the plate is attached to the outer circumferential surface of the cylinder in a state in which a proper elastic force is applied from the tongues to the second bent end portion of the plate.
When the plate is to be removed from the cylinder, the tension spindle is further rotated in the plate-attaching direction. As a result, the tongues bend such that their dimensions measured in the radial direction decrease, and the tongues disengage from the openings formed at the second bent end portion of the plate, so that the tip end portions of the tongues are released toward the deeper side of the slit. Thus, the tongues recover their original, straight shape.
When the tension spindle is rotated in the reverse direction in this state, the outwardly-facing surfaces of the tongues come into contact with the tip end of the second bent end portion of the plate and push the second bent end portion, so that the second bent end portion of the plate is pushed out of the slit. Thus, a portion of the plate located in the vicinity of the opening of the slit separates from the outer circumferential surface of the cylinder, so that a clearance is formed between that portion and the outer circumferential surface of the cylinder. The thus-formed clearance enables a worker to remove the plate from the cylinder.
The conventional apparatus for attaching a printing plate or blanket to a printing cylinder as disclosed in Japanese Patent No. 2956026 has the following drawbacks.
1. As described above, after the plate to be attached to the cylinder is inserted into the slit formed in the cylinder, the tension spindle is rotated in order to cause the tip ends of the elastic tongues to enter the openings formed in the second bent end portion of the plate. However, if the plate is inserted into the slit with a slight shifting, the tongues fail to enter the openings, because the openings and the tip ends of the tongues each have a square shape, and the relative position between each opening and a corresponding tongue is determined through engagement between opposite side edges of the opening and the opposite side edges of the tongue. In such a case, since the plate cannot be attached, the work of inserting the plate into the slit of the cylinder must be performed again. When the width of the openings formed in the second bent end portion of the plate is increased in order to overcome the above-mentioned problem, the attachment position of the plate varies greatly, which also requires re-performance of the work of inserting the plate into the slit of the cylinder. In either case, the burden imposed on a worker increases.
2. The slit formed in the cylinder is located outside of the tension-spindle insertion hole also formed in the cylinder; one of the side wall surfaces is tangent to the wall surface of the tension-spindle insertion hole; and cutaways extending in the circumferential direction are formed between the slit and the tension-spindle insertion hole at appropriate positions in order to connect the slit and the hole.
The second bent end portion of the plate inserted into the slit is located on the outside of the outer circumference of the tension spindle inserted into the tension-spindle insertion hole.
Subsequently, the plate is pulled toward the deeper side of the slit through use of elastic deformation of the tongues projecting from the outer circumferential surface of the tension spindle. Further, when the tension spindle is rotated further for removal of the plate, the tongues are disengaged from the plate and released toward the deeper side of the slit. Subsequently, the tension spindle is rotated in reverse in order to push the plate out of the slit by means of the tongues.
However, when the tongues attached to the tension spindle bend or deform permanently due to repeated plate attachment/removal operations, there is a possibility that the plate cannot be attached to the cylinder while receiving a constant tension from each of the tongues, due to variation in deformation amounts among the tongues. Further, there is a possibility that the tip ends of some tongues, having deformed greatly, do not come into contact with the plate and become unable to pull the plate into the slit and push the plate out of the slit.
Further, deformation and breakage of the tongues occur at a relatively high frequency, work of replacing the tongues and work for maintaining and inspecting the tension spindle consume a large amount of time, which lowers work efficiency.
Further, the combined shape formed by the slit and the tension-spindle insertion hole is relatively complex, and therefore a prohibitively long time is needed to machine the slit and the tension-spindle insertion hole.
An object of the present invention is to provide an apparatus for attaching an object (i.e. a printing plate or blanket) to a cylinder of a printing press, which apparatus enables attachment of the object even when the object is inserted into a slit of the cylinder with slight shifting to thereby eliminate the necessity of re-performing the insertion operation.
Another object of the present invention is to provide an apparatus for attaching an object (printing plate or blanket) to a cylinder of a printing press, which apparatus prevents deformation or breakage of a member used for pulling the object toward the deeper side of the slit and pushing the object out of the slit; enables the object to be attached to the outer circumferential surface of the cylinder under constant tension; and can reliably push the object from the slit of the cylinder for removal of the object.
Still another object of the present invention is to provide an apparatus for attaching an object (printing plate or blanket) to a cylinder of a printing press, which apparatus can reduce the frequency of repair, maintenance, and inspection work.
A further object of the present invention is to provide an apparatus for attaching an object (printing plate or blanket) to a cylinder of a printing press, which apparatus can simplify the combined shape formed by a slit and a tension-spindle insertion hole, to thereby facilitate the machining of the slit and the tension-spindle insertion hole.
To achieve the above-described objects, the present invention provides an object attachment apparatus of a printing cylinder which is adapted to anchor edge portions of an object (printing plate or blanket) located at opposite ends thereof in a winding direction of the object, after the object is wound around the outer circumferential surface of the printing cylinder. The object attachment apparatus comprises an anchor-shaft hole, a groove, an anchor shaft, and rotational force imparting means.
The anchor-shaft hole is formed in the printing cylinder in the vicinity of the outer circumferential surface thereof such that the anchor-shaft hole penetrates the printing cylinder in the axial direction.
The groove is also formed in the printing cylinder such that the groove extends outward from the anchor-shaft hole and opens at the outer circumferential surface of the printing cylinder to thereby provide a gap into which the opposite end edge portions of the object can be inserted. One of wall surfaces of the groove intersects, at an acute angle, with a tangent plane passing through a line of intersection between the wall surface and the outer circumferential surface of the printing cylinder, thereby forming an edge together with the outer circumferential surface of the printing cylinder.
The anchor shaft is rotatably inserted into the anchor-shaft hole with a proper clearance formed therebetween. The anchor shaft is partially cut away in order to form an axially extending cutaway, thereby preventing the outer circumferential surface of the anchor shaft from interfering with the object, which is inserted into the groove when the anchor shaft is positioned at a predetermined angular position. The cutaway has first and second surfaces. The first surface faces but is separated from the object when it is inserted into the groove with the anchor shaft being positioned at the predetermined angular position. When the anchor shaft is rotated from the predetermined angular position, the second surface comes into contact with the tip end of the object inserted into the groove. A plurality of pins are studded in the first surface of the anchor shaft such that they are aligned in the axial direction at an interval smaller than the length of the end edge portion of the object. The top end of each pin can engage the object when the anchor shaft is rotated from the predetermined angular position. At least a portion of the outer circumferential surface of the pin facing the second surface side has a curved shape.
The rotational force imparting means imparts a rotational force to the anchor shaft such that the anchor shaft rotates in such a direction that the second surface of the cutaway of the anchor shaft moves away from the opening of the groove and the tip ends of the pins come into contact with the object inserted into the groove.
The present invention further provides an object (printing plate or blanket) which is attached to the printing cylinder by use of the object attachment apparatus of the present invention. The object has plate portions at parallel edge portions at the opposite ends in the direction in which the object is wound around the printing cylinder. One of the plate portions is bent at an acute angle, and the other plate portion is bent at an obtuse angle, which is substantially the supplementary angle of the acute angle. The dimension of the second bent portion in the winding direction is greater than that of the first bent portion, and at least one hole is formed in a portion of the second bent portion exceeding the dimension of the first bent portion. At least a portion of the hole facing the corresponding end edge has a curved shape.
When the object attachment apparatus and the object according to the present invention are used, an operator can attach the object to the printing cylinder even when the object is inserted into the groove of the cylinder with a slight shift to thereby eliminate the necessity of re-performing the insertion operation. Further, the projecting portion of the anchor shaft which engages the object and pulls it to the deeper side of the groove does not deform or break, and the object can be attached to the outer circumferential surface of the printing cylinder under uniform tension.
Further, when the object is to be removed from the printing cylinder, the object can be reliably pushed out from the groove of the printing cylinder through a simple operation. In addition, since the mechanism is simple and does not require frequent repair, maintenance, and inspection work, the burden imposed on a worker can be reduced, and work efficiency can be increased.
Moreover, since the combined shape formed by the anchor-shaft hole and the groove for receiving the end portions of the object is simple, machining of the groove and hole can be facilitated, and costs can be reduced.